This disclosure relates generally to lighting, and embodiments of the disclosure include techniques for fabricating a large area non-polar or semi-polar gallium and nitrogen containing substrates using nucleation, growth, and coalescing processes. The disclosure can provide substrates for LEDs for white lighting, multi-colored lighting, flat panel displays and other optoelectronic devices.
In the late 1800's, Thomas Edison invented the light bulb. The conventional light bulb, commonly called the “Edison bulb,” has been used for over one hundred years. The conventional light bulb uses a tungsten filament enclosed in a glass bulb sealed in a base, which is screwed into a socket. The socket is coupled to AC power or DC power. The conventional light bulb can be found commonly houses, buildings, and outdoor lightings, and other areas requiring light. Unfortunately, the conventional light bulb dissipates about 90% of the energy used as thermal energy. Additionally, the conventional light bulb routinely fails often due to thermal expansion and contraction of the filament.
Solid state lighting techniques are known. Solid state lighting relies upon semiconductor materials to produce light emitting diodes (LEDs). Red LEDs use Aluminum Indium Gallium Phosphide or AlInGaP semiconductor material. Most recently, Shuji Nakamura pioneered the use of InGaN materials to produce optoelectronic devices emitting light in the violet, blue, and green color range for LEDs and laser diodes. The blue and violet colored LEDs and laser diodes have led to innovations such as solid state white lighting.
GaN-based devices fabricated on bulk GaN substrates with nonpolar or semipolar crystallographic orientations have been shown to have certain favorable characteristics, such as improved efficiency at high current densities and/or elevated temperatures. Most such substrates, however, have been limited in size, with lateral dimensions of about 5 mm wide by 15 mm long. This size limitation, together with relatively high cost, has significantly limited the development and implementation of nonpolar and semipolar GaN-based devices. What is needed is a cost effective means for fabricating large area nonpolar and semipolar bulk GaN substrates, together with methods for fabricating high performance, low cost LEDs and laser diodes on these substrates.